Conventionally, measurement of the amount of an analyte in a sample using a redox reaction has been utilized for a wide range of applications. For example, such measurement has been utilized for measuring glycated proteins in applications such as biochemical analyses, clinical tests, and the like.
For example, glycated proteins in blood, especially glycated hemoglobins in erythrocytes, serve as important indexes in the diagnosis, treatment, etc. of diabetes, because they reflect the patient's past history of blood glucose levels. Such glycated proteins in erythrocytes are measured utilizing a redox reaction, for example, in the following manner.
First, erythrocytes are hemolyzed to prepare a sample. Then, this hemolyzed sample is treated with a fructosyl amino acid oxidase (hereinafter referred to as “FAOD”) so that the FAOD acts on a glycation site of a glycated protein to form hydrogen peroxide. The amount of the hydrogen peroxide corresponds to the amount of the glycated protein. Subsequently, a peroxidase (hereinafter referred to as “POD”) and a reducing agent are added to the sample, so that a redox reaction occurs between the hydrogen peroxide and the reducing agent with the POD as a catalyst. At this time, when a reducing agent that develops color when it is oxidized is used, the amount of the hydrogen peroxide can be determined by measuring the color developed. As a result, the amount of the glycated protein in the erythrocytes can be determined.